Mechanisms of Foraging in Mammalian Herbivores: New Models of Functional Response

Spalinger, Donald E.; Hobbs, N. Thompson

doi:10.1086/285415

Cited by 418 publications

(452 citation statements)

References 71 publications

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“…More specifically, bipedal standing enables goats to consume browse that is not accessible to sheep. Furthermore, sheep have a less mobile mouth than goats, and are therefore less capable of selecting plant items [48,49]. Sheep are also less capable of consuming kermes oak due to the mechanical and chemical defenses (spines, tannin content, etc.)…”

Section: Discussionmentioning

confidence: 99%

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

Karmiris

Nastis

2010

Open Life Sciences

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Seasonal diets of goats, sheep and European hares (Lepus europaeus) were examined using microhistological analysis of feces collected when these herbivores grazed together in a typical Mediterranean shrubland. Approximately half of the total diet content of goats was shrubs (mainly kermes oak, Quercus coccifera), while that of hares was grasses (mostly brush grass, Chrysopogon gryllus). Sheep had a more balanced diet consisting mainly of grasses, forbs, and shrubs. Dietary overlap between goats and sheep was high throughout the year. In contrast, there was very low dietary overlap between small ruminants and hares. Dietary diversity was high in spring and low in winter across all species, with sheep in general displaying higher dietary diversity across all seasons than goats and hares. Goats had intermediate and hares had low dietary diversity across all seasons. Communal grazing by small ruminants and hares ensures that there is a more uniform use of the available forage resources than if a single herbivore is left to graze an area.

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Section: Discussionmentioning

confidence: 99%

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

Karmiris

Nastis

2010

Open Life Sciences

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“…instantaneous predation rate in relation to prey density (Holling 1959), have direct consequences for the understanding of ecological processes at the individual level, such as the role of dominance and interference on foraging efficiency (Goss-Custard et al 1984, Stillman et al 1996, Norris and Johnstone 1998, and to evaluate the role of these individual differences at the population level (Rubenstein 1981, Goss-Custard et al 1995, Piersma et al 1995. There are several mechanisms that can generate the various functional responses, particularly the asymptotic part: the competition between handling and searching for a prey, but also the interference between harvesting food and the velocity of the animal, or the competition between cropping and processing food (see Spalinger and Hobbs 1992 for the theoretical approach on herbivores). The understanding of the shape and parameters of the functional response can thus allow for the testing of hypotheses related to processes limiting intake rate (Gross et al 1993).…”

Section: H Fritz D Durant and M Guillemain Cnrs-upr 1934 Centrementioning

confidence: 99%

Shape and sources of variations of the functional response of wildfowl: an experiment with mallards, Anas platyrhynchos

Fritz¹,

Durant²,

Guillemain³

2001

Oikos

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Understanding the variations of the functional response of an organism, i.e. the predation rate in relation to prey density, is necessary to understand the interactions between the animal and its food supply. This has received little attention in dabbling ducks so we investigated experimentally the shape of the functional response of mallard feeding on poultry pellets, and assessed the influence of several factors such as the size of food items, sex or individual performance on this functional response. Individual differences in intake rate are of crucial importance in group or gregarious foraging species. We used two approaches of the functional response: 1) the relation between feeding rate (pellets/s) and pellet densities (pellets/m 2 ), and 2) the relationship between instantaneous intake rate (g/s) and biomass density (g/m 2 ). For both approaches, we found that the Type II functional response gave better estimates than a Type I linear functional response but explained only a third of the variance. Our results show that pellet size has a large effect on instantaneous intake rate. The comparison of the functional response parameters suggest that handling time per prey may not reflect the real constraints on intake rate, but that handling time per gram ingested may be more appropriate to integrate the effect of item size in the functional response. We then discuss the possible mechanisms involved. We also found individual variations in the functional response for each of the experiments, with some consistency in the hierarchy regarding feeding efficiency. We did not find any differences between males and females. Our results provide an evaluation of individual variations in intake rate in interference-free conditions, which has rarely been done, and call for more controlled experiments to allow a finer understanding of the mechanisms of food acquisition in dabbling ducks.

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“…Examination of the mechanisms responsible for forage intake rates of mammalian herbivores [36] reveals that intakes of mammalian browsers are often poorly related to food biomass. The models constructed to illustrate intake rates of caribou (Rangifer tarandus), black-tailed deer and moose (Alces alces) suggest relatively constant intake rates across a wide range of plant biomass and a sharp drop in these rates when the plant biomass is near 0 [37][38][39]. This is a pattern exhibited by the perfect forager ( Figure 5).…”

Section: Discussionmentioning

confidence: 93%

What elk, wolves and caterpillars have in common—The perfect forager theorem

Weclaw¹,

Hudson²

2013

OJE

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It is widely accepted that the Marginal Value Theorem (MVT) describes optimal foraging strategies of animals and the mechanism proposed by the MVT has been supported by a number of field observations. However, findings of many researchers indicate that in natural conditions foragers do not always behave according to the MVT. To address this inconsistency, in a series of computer simulation experiments, we examined the behaviour of four types of foragers having specific foraging efficiencies and using the MVT strategies in 15 different landscapes in an ideal environment (no intra-and inter-specific interactions). We used data on elk (Cervus elaphus) to construct our virtual forager. Contrary to the widely accepted understanding of the MVT (residence time in a patch should be longer in environments where travel time between patches is longer) we found that in environments with the same average patch quality and varying average travel times between patches, patch residence times of some foragers are not affected by travel times. Based on our analysis we propose a mechanism responsible for this observation and formulate the perfect forager theorem (PFT). We also introduce the concepts of a foraging coefficient (F) and foragers' hub (α), and propose a model to describe the relationship between the perfect forager and all other forager types.

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Mechanisms of Foraging in Mammalian Herbivores: New Models of Functional Response

Cited by 418 publications

References 71 publications

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

Shape and sources of variations of the functional response of wildfowl: an experiment with mallards, Anas platyrhynchos

What elk, wolves and caterpillars have in common—The perfect forager theorem

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